The invention relates to a method of setting up connections for the transfer of information in the form of calls between a calling and a called subscriber in a teletransmission network, where each subscriber is connected to the network via a subscriber interface, and where, on the basis of an identification associated with a given call, it is detected whether the call is of a first or of a second type. In case of calls of the first type, the connection is set up via a first transmission path which comprises one or more exchanges, while in case of calls of the second type, the connection is set up via or switched to a second transmission path. The invention moreover relates to a detector unit for use in connection with the method.
Connections are traditionally set up via telephone exchanges in such transmission networks. When a subscriber wishes to get connected to a second subscriber, a connection is first set up from the first subscriber to the exchange to which he belongs, and then the exchange sets up a connection to the second subscriber. In case of local calls the latter connection will be directly from the exchange to the subscriber. In other cases, the connection goes via one or more other exchanges. Thus, it is an exchange which provides for the setting up of the connection, and moreover a connection from the first subscriber via one or more exchanges to the second subscriber will be occupied during the call.
Today the telephone network is not only used for the transmission of ordinary telephone calls, but also for different forms of data transmission (electronic mail, ISDN, etc.). In this connection it is known to transfer data between two data terminals connected to the network without the assistance of the traditional telephone exchanges, as, in such situations, the connection is instead set up by means of special exchanges or set-up units adapted for the purpose. Of course, this form of transmission requires that the network lends itself to this, and will therefore occur particularly in more recent network types composed of e.g. optical fibres, where the transmission can typically take place according to a system of a digitally designed hierarchy (e.g. SDH or PDH). This network type must be extended all the way to each subscriber or data terminal in this case, which is usually not the case. The data terminals must moreover be equipped with an interface to the transmission system concerned. This form of data transfer is therefore a rather expensive solution, which is of interest only to subscribers having a great need for data transmission. The data themselves will typically be transferred by means of a protocol which is specially adapted for the purpose, such as e.g. ATM (Asynchronous Transfer Mode) or ISDN.
In this connection it is known from GB 2 132 446 to arrange an exchange such that it is capable of handling two or more network layers, one of which may be for the normal telephone traffic, and the other may be for e.g. ISDN traffic or telex traffic.
Where a subscriber wishes to be able to transfer both ordinary telephone calls and data in the manner described, it will often be necessary to have two separate terminals and two separate connections to the network, and this in turn necessitates a sufficiently great data transmission need. Usually, the telephone exchange is connected to the network via an ordinary cable twisted in pairs, while the data terminal may be connected e.g. via an optical fibre cable.
Where the data transmission need is smaller, data terminals may instead be connected to the network via a modem and the ordinary telephone interface. This leads to a sort of hybrid calls, as these data transmissions are processed as ordinary telephone calls in the entire network and are converted into data again by means of a modem only at the receiver terminal.
These hybrid calls occur in rapidly increasing numbers and therefore occupy an ever greater part of the capacity of the exchanges and of the network itself. One reason is that new types of calls are generated. This applies to i.a. so-called Internet calls, which occur, because subscribers to the Internet, which is an international data network, are usually connected to it via the ordinary public telephone network. Subscribers to the Internet use a personal computer (PC) and a modem, and an Internet call is set up therefrom via the telephone network and the exchanges thereof to an Internet service provider, where it is likewise received by a modem and coupled to the Internet itself.
These calls are typical local calls, as the distance to the closest service provider is usually relatively short. Further, the calls are typically very long compared to the usual telephone traffic, and a connection is maintained during the entire call from the subscriber via one or more exchanges to the Internet provider, even though this connection is utilized poorly since there may be long pauses where no data are transmitted. When data are transmitted, then a high quality of the connection is required in order to avoid frequent retransmissions.
Thus, the problem is that these hybrid calls, transmitted in the network as ordinary telephone calls, occupy an excessively great capacity at the exchanges as well as in the network itself. As the use of both the Internet and other corresponding new types of transmission must be presumed to increase rapidly, there is thus a great need for extending the capacity of the existing networks, which i.a. calls for investments in new exchanges and extension of the existing ones.
European Patent Application EP 0 621 714 discloses a system wherein it is established in a high level exchange (toll switch) on the basis of calling information, derived from the called telephone number, whether a call is of a special type, in this case a toll free call to a voice response system. In that case, the call in the high level network, which connects the high level exchanges, may be processed in another manner than the normal calls, thereby allowing the call toll for such calls to be reduced. Since, however, the switching exclusively takes place in the high level network, it does not reduce the load on the subscriber exchanges and the networks connecting these to the individual subscribers, and, as mentioned, since the described Internet calls will typically be local calls, it is precisely here that the mentioned problems of capacity occur.
The invention is based on the finding that a great part of the new traffic, such as e.g. the Internet calls, in reality does not have to be set up via the exchanges at all; but may instead be processed in the greatest part of the network in the same manner as the above-mentioned direct data transfer between subscribers with a great data traffic.
The object of the invention is to provide a solution which is capable of giving a considerably increased capacity in the existing telecommunications network, without requiring the mentioned new investments in new exchanges or investments in expensive interface equipment at the subscribers.
This is achieved according to the invention in that the detection of the type of the call takes place at the subscriber interface of the calling subscriber, and that said second transmission path bypasses said exchange or exchanges.
This ensures that calls of the first type, which may e.g. be the ordinary telephone calls, are set up in the usual manner via the conventional telephone exchanges, while calls of the second type, which may e.g. be data calls, may be set up directly without the assistance of the exchanges. This means that these calls, the number of which may be expected to increase rapidly, as mentioned, need not occupy capacity at the exchanges, thereby making a greater capacity available to other calls.
When, as stated in claim 2, the detection of the type of the call takes place during the initial phase of the call, both the set-up and the entire subsequent call may be kept out of the exchanges, which are therefore loaded as little as possible.
In an alternative embodiment, the detection of the type of the call may take place at any time during the call. This involves the advantage that also calls changing type during the call may be set up via the most expedient path in the network. Further, it allows all calls to be set up as ordinary calls from the beginning, and that just calls which turn out to be e.g. data calls in reality, are set up via the direct route bypassing the exchanges.
As stated in claim 4, a particularly expedient field of use of the invention is calls to subscribers offering a specific service on the telephone network. In that case, the detection of the type of the call may take place by checking the telephone number to which the call concerned is made, as stated in claim 5. If the telephone number called corresponds to the number of the provider of the service concerned, the call is set up directly through the said second transmission path, while in all other cases it is set up in the traditional manner by means of the exchanges. Alternatively, as stated in claim 3, the detection may take place by detecting the information type of the call.
As stated in claims 6 and 7, the special service may be of the type which allows a telecommunications network subscriber to be connected to it via a second network, which may e.g. be the Internet.
Further, if, as stated in claim 8, data are transferred via the second transmission path by means of a protocol which just occupies capacity on the network in relation to the data amount transferred at a given time, it is ensured not only that the exchanges are free from these calls, but also that the network itself is loaded only when data are actually transferred. Since in particular the said Internet calls frequently have long periods where just few or no data at all are transferred, it is thus ensured that the network is practically not loaded during these periods, resulting in a far better utilization of its capacity.
The method is particularly expedient when, as stated in claims 10 and 11, it is used in a fibre-optical network where the transmission may take place according to a Synchronous Digital Hierarchy (SDH system), and where the second transmission path in the network is embedded in the SDH transmission by a special protocol for the transfer of data. As stated in claim 9, this protocol may be of the Asynchronous Transfer Mode (ATM) type, which is a protocol which just occupies capacity on the network in relation to the amount of data transferred.
When the part of the network connected to the subscribers from whom calls may be made, consists of cables twisted in pairs and having metallic conductors, while the rest of the network is substantially a fibre-optical network, the detection of the type of the call may expediently take place at an interface between the cable of the subscriber and the fibre-optical network, as stated in claim 12. This provides the shortest path in the network for the calls bypassing the exchanges, as the detection takes place as close to the subscriber as possible.
Alternatively, as stated in claim 13, at least some of the subscribers from whom calls may be made, may be connected to the network via a wireless connection, and the detection of the type of the call may take place at an interface between the wireless connection and the wired connection.
As mentioned, the invention also concerns a detector unit for use in the setting up of connections in a network of the stated type. When, as stated in claim 14, the detector unit is adapted to detect the type of the call at the subscriber interface of the calling subscriber and to set up said second transmission path bypassing said exchange or exchanges, then the above-mentioned more expedient setting-up of the calls of the second type, which may e.g. be data calls, is achieved.
The detector unit may either be adapted to detect the type of the call during the initial phase of the call by comparison with known telephone numbers, as stated in claim 15, or it may be adapted to detect the type of the call during the call by detecting the information type.